* docs: adjust page heading levels
Only the page TOC should be at heading level 1. All other headings
should start at level 2. This commit also removes duplicate headings,
in continuation of #2796.
(This fix is necessary to support an auto-TOC feature.)
* lifecycle-hooks: copy latest to cache
* docs(lifecycle-hooks): post-RC5 Dart resync
- TS prose: removed mention of `routerOnActivate` which no longer
exists in the new router.
- TS improvements to the sample code have also been propagated to the
Dart sample.
Contributes to #2077.
E2E tests pass now.
* post-review updates
